1. Field of the Invention
The invention relates to the field of communication networks and, more particularly, to the management of subrate paths in an optical network.
2. Description of the Related Art
The optical carriers in many optical communication networks have greater data transfer capabilities than one site or customer can reasonably use. For this reason, it is advantageous to be able to provision multiple paths through the same optical carrier. The provider of an optical communications network will frequently choose to employ some form of wavesharing in order to partition and sell lower capacity paths through the network. One method of wavesharing is time-division multiplexing using payload timeslots, such as the Synchronous Digital Hierarchy (SDH) or Synchronous Optical Networking (SONET) standards. The SONET standard defines a hierarchical method of byte-interleaved multiplexing. The hierarchy supports carriers handling varying capacities and defines overhead and payload bytes for network management and fault detection.
Under the SONET standard, data is transferred between nodes using a plurality of subrate timeslots. Generally, subrate add/drop multiplexors (ADMs) in the node elements of a given network will define the number and capacity of subrate timeslots available for paths between nodes. The underlying optical communications network defines the general topology and capacity in which the subrate network operates. The ADMs define the hierarchy of subrate capacities and the subrate topology overlaying the carriers in the optical communications network. The topology of the ADMs generally mimics the underlying network topology. If the underlying network topology is a ring of interconnected nodes, the subrate timeslots may follow a similar ring topology. However, some optical nodes may not be equipped with ADMs, and are therefore transparent to the subrate network. The capacity of underlying optical channel is divided into a number of subrate timeslots, as defined by the ADMs. The individual timeslots determines the minimum capacity subrate path available. For example, if the underlying capacity of the carrier is ˜2,488 Mbps and the node elements support 48 subrate timeslots, each timeslot has a capacity of ˜52 Mbps. Higher capacity paths are created by provisioning groups of the individual timeslots and aggregating their capacities. Note that a subrate path need not utilize the same timeslot through the entire network, but it must leave one node and be received by an adjacent node using the same timeslot. Provisioning subrate paths involves identifying the timeslots through which each ADM node in the path is receiving and sending data, and properly setting the cross-connects in each node to route the data between the identified timeslots.
Nodes in an optical communications network may typically be associated with an administrative complex. The administrative complex includes an administrative node processor module (ANPM) having a processor and a primary database. The administrative complex is concerned with control of administrative functions, examples of which include configuring and monitoring elements of a node and providing a management interface to a user. The administrative functions also include assigning timeslots within a node and establishing the appropriate cross-connects. A key part of monitoring the network includes the ability to determine the existing band, channel, and timeslot allocations in a network and the status of such bands, channels, and timeslots.
A network may comprise many nodes, and each of the nodes may have an associated administrative complex. Each of the administrative complexes is communicatively coupled to a network management application that is used by personnel at a network operations center (NOC) who are responsible for monitoring and managing the entire network. Typically, information such as the status of a particular channel, the nodes that a channel couples (or circuits that have been provisioned), operations that are performed at a node, alarm states, administrative states of circuits, as well as other detailed information about the network is provided by the administrative complexes to the NOC. Users at the NOC typically formulate requests for information, send those requests to the administrative complexes, and receive responses from the administrative complexes on an as needed basis. In a similar manner, such information can be gathered as the network is configured, periodically once the network is operational, and at times when there are failures in the network.
The provisioning of subrate paths includes identifying the node elements through which the path will go, identifying the available subrate timeslots for entering and leaving those node elements, and setting the proper cross-connects for directing data between receiving and sending timeslots within the node elements. In some node elements, such as ADMs, the timeslots include line timeslots for connections between adjacent node elements and tributary (or trib) timeslots for connections between node elements and destinations outside the network (e.g. a user site or another network). In some network configurations, the line timeslots include eastward timeslots for connecting to a node element's east neighbor and westward timeslots for connecting to a node element's west neighbor. Cross-connects may connect a trib timeslot to an eastward or westward line timeslot (add or drop), an eastward line timeslot to a westward line timeslot (pass through), or two trib timeslots to one another (hairpinning). A simple path will include a first end node with an add/drop configuration, a second end node with an add/drop configuration, and a number of intermediate nodes with pass through configurations.
In order to provision the cross-connects for a path in a SONET network, matching timeslots in adjacent nodes need to be identified. The fiber between node elements does not manipulate that data that passes through it. Data that is sent in a particular timeslot from one node will be received via the same timeslot at an adjacent node. Thus, adjacent nodes must have matching timeslots provisioned in order to correctly transfer data between them. For example, if node A is sending data out through its eastward timeslot 17, adjacent node B must have its westward timeslot 17 provisioned to receive the data. Because a SONET topology may have a variety of paths routed through it, with varying entry and exit nodes, not all node elements will include the same paths as their neighbors. As the number of provisioned paths in the network increases, identifying available channels and provisioning the corresponding timeslots may become increasingly difficult.
In most subrate networks, paths are bi-directional. A single provisioned timeslot represents a two-way circuit. Multiple timeslots may be provisioned to provide a higher capacity path. Additional paths may need to be provisioned depending upon any protection schemes that are in place for the service. For example, a service in a ring topology may use bi-directional protection, requiring circuits to be provisioned in both directions around the ring. Similarly, various forms of trib protection may influence the provisioning of a service. Consideration of protection schemes further increases the complexity of provisioning services in an optical communications network.
Prior methods of provisioning a service required a network administrator to gather and understand a great deal of information in order to provision a new service. First, the network administrator would receive an order for a new service for a particular customer. The new order would specify the sites to be connected, any trib and line protection being used, and the capacity desired. Based upon the identified sites, the network administrator would determine which nodes would be in the circuit. The nodes may also vary depending upon the type of line protection requested. The network administrator would then issue a query to each of the nodes to discover what timeslots were currently available in each. Once replies to the queries were received, the network administrator would evaluate the information and identify available paths for the service. The network administrator would then select paths based upon the desired capacity. Based on the selected paths, the network administrator would then issue an order to each of the nodes specifying the proper configuration of the cross-connects. In some networks, setting the cross-connects may need to be done on-site at the nodes, rather than through the network. Once the network administrator has received confirmation that the cross-connects are set, the circuits in the new service are tested. If testing is successful, the new service is turned over to the customer.
Unfortunately, the prior methods involve a great deal of time and effort by the network administrator. The administrative complexes provide timeslot discovery information and cross-connect confirmation in a piecemeal basis that makes it very difficult to get the correct information to configure the network. Moreover, it causes the NOC to issue repeated requests for the same information. Thus, there is a need for a method to provide information necessary for provisioning and maintenance of subrate services in a more readable and useful manner.
Therefore, it is desirable to have a system for displaying subrate path provisioning information to a user. It is also desirable to have a system that allows a user to easily provision and maintain subrate services. Some degree of automation for provisioning of the nodes for an identified subrate service is also desirable.